Hi there Phindile,
One of our top mechanical lecturers (Herman van der Merwe) has done a tutorial to assist you using the slides you sent through. He is feeling ill but was there for his part time students this evening – excuse his croaky voice.
With an assembly you are usually given a number of individual components which you are required to assemble in a drawing.
First look for the part that will be your base (it may have a footing) as all the other components will then build onto this.
The most important thing to look for then is common sizes: bolt holes, shafts etc. indicating how they will assemble.